Stock mkt ratios

What is the definition of Piotroski F-Score?
The Piotroski F-Score is a nine-criteria scoring system developed by financial academic, Joseph Piotroski in a famous research paper. Each of the nine points relate to the change in a ratio based on the company's accounts.
Companies with a score of 8 or 9 have been found as a group to outperform weak stocks by 7.5% annually over a 20 year period. The weakest stocks, scoring 2 or lower, were found by Piotroski to be five times more likely to fall into financial problems.
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